by Lindsay H. Jones, USA TODAY Sports

by Lindsay H. Jones, USA TODAY Sports

RENTON, Wash. -- Earl Thomas has his headphones on as he sits inside his locker, slightly bobbing his head. He directs a piercing glare at no one in particular.

He stands, pulls his white No. 29 jersey over his head, and slips a compression sleeve up his left arm. Thomas sits, glaring menacingly some more.

The heart of the Seattle Seahawks' nasty defense is pumping himself up.

For practice.

"He's one of the most locked-in football players I have ever seen," cornerback Richard Sherman said Thursday. "He's the type of player that makes unbelievable plays look routine daily."

Through the first half of the season, no defensive player in the NFL has been better than Thomas. It's clear the Seahawks' salty attitude and physical play comes straight from their powerful free safety.

"This year is special, it's magic," Thomas said. "You can just feel it."

For all of the offseason buzz about quarterback Russell Wilson, the Seahawks are a Super Bowl contender because of Thomas and the defense â?? a group that, save Thomas, is composed mostly of outcasts and underdogs.

"That's what our team is built on," cornerback Brandon Browner said. "When coach [Pete] Carroll came in from USC, they gave a lot of second-chance guys that opportunity to play football again."

Since Carroll and general manager John Schneider arrived together in 2010, they have overhauled the defense. Only two players, end Red Bryant (2008) and tackle Brandon Mebane (2007), remain from the Mike Holmgren-era Seahawks.

Six the Seahawks' defensive starters have been drafted since, a haul that includes first-rounders in Thomas (2010) and outside linebacker Bruce Irvin (2012) and hits on a couple of fifth-rounders, Sherman (2011) and safety Kam Chancellor (2010).

Seattle made smart trades, too, such as a 2010 deal with Philadelphia to get pass rusher Chris Clemons (37 sacks since). It culled savvy free agent additions, including signing Browner out of the Canadian Football League to a futures contract in 2011. It corrected past mistakes, such as re-signing defensive end Michael Bennett this year. Bennett was waived as a rookie after three games in 2009 and claimed by Tampa Bay.

"I think they are trying to find the most talented players with the biggest chip on their shoulder," second-year middle linebacker Bobby Wagner said. "You know, somebody that has something to prove, someone that [Carroll and Schneider] know, if they get in the league, they'll always have that chip on their shoulder."

The result has been a unit that ranks second in total defense (289.2 yards per game) and third against the pass (184.1).

Wagner was a second-round pick, but he believed he was downgraded by NFL teams because, at 6-0, 241 pounds, he isn't the size of a prototypical middle linebacker. But Wagner said his chip began well before the draft, when as a senior in high school he received only one Division I offer, to Utah State.

Those types of slights don't die easily, said Browner, who might have the biggest chip of any of Seahawk. Browner was signed to play safety by the Denver Broncos as an undrafted rookie in 2005, arriving in a rookie class that included three defensive back draft picks. He spent his rookie year there on injured reserve and was released after training camp in 2006.

When no other NFL offers came, Browner became an all-star for the Calgary Stampede in the CFL. He won a championship during his four seasons there, but never got over the feeling the NFL had overlooked him.

"I was capable enough to make somebody's roster, let alone start for one of those teams," Browner said.

Browner was part of Carroll's quest in 2011 to bulk up at cornerback, a belief that size on the outside was just as important as speed. That offseason, the Seahawks added Browner and Sherman, who have combined with Thomas and Chancellor to become arguably the NFL's best secondary.

Sherman can rattle off the names of all of the cornerbacks drafted ahead of him in 2011. Even Thomas, an All-American at Texas, has found ways to take perceived slights and turn them into motivation. He currently focuses on that fact he isn't often mentioned in the conversation for the league's defensive MVP.

It's a legitimate beef after four interceptions, two forced fumbles and 57 total tackles in eight games â?? the best player on one of the league's best defenses.

"You can get lost in the shuffle, and before you know it, they're saying it's another guy, and you could have been doing this all along," Thomas said. "We'll see. We'll see how this year goes. I'm going to keep proving them wrong."